(1) Technical Field
The present invention relates generally to an apparatus and method useful in measuring properties of an ion beam and more particularly to an apparatus and method for performing functions of both a Faraday and an energy contamination monitor.
(2) Related Art
A Faraday Cup, or Faraday, measures an ion beam current by drawing an electron from ground for each positive ion that enters it. The Faraday's magnetic field prevents external secondary electrons from entering and prevents produced secondary electrons from exiting, thus enabling a measure of the current of the ion beam itself, free from the influence of extraneous charged particles.
An energy contamination monitor detects ions in a decelerated ion beam that have become neutral. Adjustment of an ion implanter in response to the detection of such ion beam neutrals permits their reduction or elimination before being implanted on a wafer. Energy contamination monitors are described more fully in co-pending U.S. Provisional Patent Application Ser. No. 60/544,029, which is hereby incorporated herein by reference.
Instrumentation in the end-station of an ion implanter is required to perform a variety of measurements, including the dose being applied to a wafer, the angular distribution of the ions within an ion beam, the density distribution of the ions within the ion beam as a whole, and the level of energy contamination in decelerated ion beams. To perform these measurements, an end-station typically includes both a Faraday and an energy contamination monitor, increasing both the physical hardware and expense of the end-station. Accordingly, there is a need in the art for an apparatus and method for performing a function of each of a Faraday and an energy contamination monitor, thus reducing both the hardware and expense of an ion implanter end-station.